Deployment system for an upper bundle steam generator cleaning/inspection device

ABSTRACT

A deployment system for an upper bundle steam generator cleaning/inspection device, the deployment system including an elongated body feedable through an access in a steam generator shell proximate the tube sheet of the steam generator, the elongated body flexible in one configuration to bend into a position for extension up through flow slots in support plates of the interior of the steam generator, and rigid in another configuration for positioning and supporting cleaning/inspection devices up through the steam generator proximate the upper tube bundles of the steam generator; and a drive device for driving the elongated body up through the support plates and for retracting the elongated body back down through the support plates.

RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. application Ser. No.08/239,378 filed May 6, 1994 now U.S. Pat. No. 5,564,371.

FIELD OF INVENTION

This invention relates to a deployment system for an upper bundlecleaning/inspection device for a nuclear power plant steam generator.

BACKGROUND OF INVENTION

Steam generators convert heat from the primary side of a nuclear powerplant to steam on the secondary side so that the primary and secondarysystems are kept separate. A typical generator is a vertical cylinderconsisting of a large number of U-shaped tubes which extend upward fromthe floor or “tube sheet” of the generator. Fluid at high temperatureand pressure from the reactor travels through the tubes giving up energyto a feed water blanket surrounding the tubes in the generator creatingsteam and ultimately power when the stream is introduced to turbines.

Steam generators were designed to last upwards of forty years but inpractice such reliability figures have proven not to be the case. Theproblem is that sludge from particulate impurities suspended in the feedwater forms on the tubes which greatly affects the efficiency of thegenerator and can even cause the tubes to degrade to the point ofcausing fissures in the tubes. If radioactive primary fluid within thetubes seeps into the secondary side, the result can be disastrous.Plugging or otherwise servicing such fissures is time consuming andresults in expensive down time during which power must be purchased fromother sources at great expense.

There are known methods for cleaning the tubes proximate the bottom ofthe steam generator using flexible lances and the like using water underpressure, but since a typical steam generator can be thirty feet tall,it is very difficult to reach the sludge at the upper levels of thetubes using water jets directed upwards from the bottom of thegenerator.

So, chemical cleaning is used but there are several disadvantages.First, chemical cleaning is very expensive and requires an extendedoutage. Also, the solvents used in chemical cleaning can corrode theinternal components of the steam generator. In addition, chemicalcleaning can generate large quantities of hazardous, possiblyradioactive waste. Disposal of this waste is very expensive. For thesereasons, although many utilities have considered chemical cleaning, fewplants have actually implemented it.

On the other hand, there are severe technical challenges faced whenconsidering alternate cleaning methods. A typical steam generator hasapproximately 50,000 square feet of heat transfer area. The tube bundleis about 10 feet in diameter and 30 feet tall but the access alley inthe middle of the tube bundle is only 3.5 inches wide and is interruptedby a series of successive support plates approximately every 4 feet.There are flow slots through the support plates but they are very smallin size, typically 2.75 by 15 inches. In addition, the access into thesteam generator is limited to a six inch hand hole. Finally, the gapbetween the vertically extending tubes is only 0.406 or less.

Therefore, manipulating cleaning spray heads and/or inspection equipmentup 30 feet to the top of the steam generator to clean or inspect theupper tube bundles is not trivial. There are three primary designconsiderations. First, the deployment system must be small enough so itcan fit through the hand hole of the steam generator and through theflow slots in successive support plates. Second, the deployment systemmust extend up through the flow slots to a length of as much as 30 feetwhile still providing support for the cleaning head or inspection devicedeployed at the distal end. Third, the deployment system must be fullyretractable. A system which has the potential for failure, which couldbecome lodged in the upper regions of the tube bundles, or which couldfail and leave components inside the steam generator is too risky toemploy inside the very expensive steam generators.

In addition, the deployment system must facilitate fast cleaning and/orinspection to minimize downtime with a minimum of manual labor due tothe expensive outage costs associated with nuclear power plants and thepotential hazard of radioactive exposure to workers in the area duringcleaning.

In the patent to Brooks (U.S. Pat. No. 5,265,129), a dual boom design isdiscussed wherein a telescoping portion consisting of a plurality ofpneumatic or hydraulic cylinders is used to deploy an inspection cameraup through the support plates. One problem with this design is that thetelescoping portion in its collapsed state must be received through thehand hole of the generator and then uprighted—but it cannot exceed theheight of the first tube support plate which may be as small as 18inches.

Such a device which in its collapsed state can be uprighted in an 18inch height and which is still capable of extending up to 30 feet isdifficult to design, manufacture, and control.

SUMMARY OF INVENTION

It is therefore an object of this invention to provide a deploymentsystem for an upper bundle steam generator cleaning/inspection devicewhich does not rely on telescoping cylinders.

It is a further object of this invention to provide such a deploymentsystem which allows cleaning of the steam generator to proceed from thetop down thereby flushing deposits downward during the cleaning process.

It is a further object of this invention to provide such a deploymentsystem which eliminates the need to use chemical cleaning techniques andovercomes the disadvantages inherent in chemical cleaning or which canbe used in conjunction with chemical cleaning.

It is a further object of this invention to provide such a deploymentsystem which fits through an access in the bottom of the steamgenerator, which can be protracted to extend up through the flow slotsin the support plates of the interior of the steam generator to delivera cleaning head or inspection camera to the upper bundles of the steamgenerator, and which then retracts back down through the flow slots forremoval after the cleaning and/or inspection operation is completed.

This invention results from the realization that instead of inserting adevice into the steam generator through the hand hole and then relyingon telescoping cylinders to deploy a cleaning head or inspection cameraup through the tube support plates, a suitable deployment system caninstead be constructed by using a snake-like device which is fed throughthe hand hole from the outside of the steam generator, is flexibleenough to make the 90° turn to be in position to travel upwards throughthe tube support plates, and is also rigid enough to then travel upwardsto the upper tube bundles of the steam generator (e.g., 30 feet) andstill support inspection devices or cleaning heads for inspection orcleaning the upper areas of the steam generator, and which is alsoretractable so that the inspection device or cleaning heads are safelyremoved from within the steam generator.

This invention features a deployment system for an upper bundle steamgenerator cleaning/inspection device. The deployment system may suitablycomprise, include, consist essentially of, or consist of an elongatedbody feedable through an access in a steam generator shell proximate thetube sheet of the steam generator. The elongated body is flexible in oneconfiguration to bend into a position for extension up through flowslots in support plates of the interior of the steam generator and rigidin another configuration for positioning and supportingcleaning/inspection devices up through the steam generator proximate theupper tube bundles of the steam generator. There are also some means fordriving the elongated body up through the support plates and forretracting the elongated body back down through the support plates.

The elongated body assembly typically includes means for mounting acleaning head on a terminal end thereof for cleaning the upper tubebundles of the steam generator and/or means for mounting an inspectioncamera on a terminal end thereof for inspecting the upper tube bundlesof the steam generator.

The elongated body may be a rigid chain, or a pair of rigid chains eachbendable in only one direction, each deployed into the steam generatorby bending, the pair deployed back to back in the rigid configuration.

Another type of rigid chain includes a number of links, each pivotablewith respect to an adjacent link in one configuration, the linksincluding means for releasably locking adjacent links against pivotingin another configuration. The means for releasably locking includesretractable pins for locking the links together when engaged, and forfreeing said links when retracted. In this case, the means for drivingincludes means for automatically retracting and engaging the pins.

The means for releasably locking may alternatively include detent ballson one portion of the links and complementary detent recesses on oneportion of adjacent sets of links or, the means for releasably lockingmay include a spring for urging one link to remain engaged with anadjacent link. The means for releasably locking may be a magnet forurging one link to remain engaged with an adjacent link. Also, the meansfor releasably locking may be both a spring and a magnet for urging onelink to remain engaged with an adjacent link. The rigid chain could alsobe a plurality of links each having a hinge and a portion extendingbeyond the hinge for preventing movement of an adjacent link in onedirection.

As an alternative to the rigid chain configuration, the elongated bodymay include a plurality of rigid links. The links each have a hinge andat least one articulation recess proximate the hinge for allowingmovement of an adjacent link in only one direction, or there may be anarticulation recess on each side of the hinge. The deployment system mayalso be an extendable mast formed of a material self-biased to form atube. In this case, the means for driving includes a pair ofcounter-rotating drums for driving the mast material engaged between thedrums.

The mast configuration and the rigid chain configuration or the rigidlink configuration may be combined: the elongated body comprises a rigidchain supported by an extendable mast formed of a material self-biasedto form a tube or the elongated body comprises a series of rigid linkssupported by a mast formed of a material self-biased to form a tube.

The drive means preferably includes a turning shoe for directing theelongated body from a position proximate the tube sheet to a positionfor extension upwards therefrom to the upper bundles of the steamgenerator.

DISCLOSURE OF PREFERRED EMBODIMENT

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a schematic view of a typical steam generator;

FIG. 2 is a schematic diagram of one type of cleaning head raised intoposition by the deployment system of this invention;

FIG. 3 is a schematic diagram of a combined cleaning head and inspectiondevice raised into position by the deployment system of this invention;

FIG. 4 is a schematic diagram of a deployment system according to theprior art which uses a series of telescopic cylinders;

FIG. 5 is a schematic view of the deployment system of this inventionwhich employs an elongated body flexible in one configuration and fairlyrigid in another configuration;

FIG. 6 is a schematic view of a rigid chain embodiment of the elongatedbody shown in FIG. 5;

FIG. 7 is a schematic view an embodiment including back to back rigidchains according to this invention;

FIG. 8 is a front view of a typical chain linkage;

FIG. 9 is a front view of a rigid chain used in the deployment system ofthis invention;

FIG. 10 is a front view of two rigid chains placed back to back in thedeployment system of this invention;

FIGS. 11A and 11B are schematic views of another type of rigid chainused in the deployment system of this invention;

FIG. 12 is a schematic view of still another type of rigid chain used inthe deployment system of this invention;

FIG. 13 is a schematic view of a spring biased rigid chain according tothis invention;

FIG. 14 is a schematic view of a magnetically biased rigid chainaccording to this invention;

FIG. 15 is a schematic view of a rigid chain incorporating both a magnetand a spring;

FIG. 16 is a front view of another type of rigid chain according to thisinvention;

FIG. 17 is a schematic view of a series of rigid links with a singlearticulation recess according to this invention;

FIG. 18 is a schematic view of a series of rigid links having dualarticulation recesses according to this invention;

FIG. 19 is a schematic view of a self-biased mast used in the deploymentsystem according to this invention;

FIG. 20 is another view of the self-biased mast of this inventionincluding drive means; and

FIG. 21 is a schematic view of a deployment system according to thisinvention which employs both a mast material and a rigid link structure.

FIG. 1 schematically shows steam generator 10 which includes heattransfer tubes 12 separated into sections by successive tube supportplates 12, 14, 16 18, 22, 24, and 26. Each tube support plate includes anumber of flow slots 28 and 39 as shown for first tube support plate 12.

The Westinghouse model W44 and W51 steam generators comprise the largeststeam generator market segment and the dimensions of the W51 are similarto the W44. The W44 steam generator utilizes 116″ diameter tube supportplates spaced evenly at 51″ above the tube sheet. There are two 6″diameter hand holes such as hand hole 36 at each end of the 3½″ blowdownlane 38 at the tube sheet 32 level. Each tube sheet support plate hasthree flow slots measuring 2¾″ by 15″ spaced at 4″ inches on each sideof center tie rod 40. The flow slots are aligned with respect to eachother so that there is a clear “line of sight” vertical passage from theblow down lane 38 to the U-bends 41 of the tubes above the top tubesupport plate 26.

As discussed in the Background of the Invention above, there are knowninstruments for water-spray cleaning the areas between tube sheet 32 andfirst tube sheet support plate 14 at the bottom of the steam generatorbut the very close confines within the upper bundles of the steamgenerator make cleaning the tubes near the upper support plates verydifficult. See, e.g., U.S. Pat. No. 5,265,129.

In this invention, it was realized that there is an access path 34 fromhand hole 36 along blowdown lane 38 to the center tie rod 40 and thenupwards through the aligned flow slots 28, 30, etc. in each supportplate to the top portion 42 of the steam generator. And, it was realizedthat if a cleaning head or heads could be deployed to the top portion 42of the steam generator, the generator could be cleaned from the top downthereby flushing deposits downward during the cleaning process. Thetechnical challenge is to design a cleaning or inspection headdeployment system which will fit within the close confines of theinterior of the steam generator, which is flexible enough to make the90° turn shown at 31, which is rigid enough to then travel upwards tothe upper bundles 42 of the steam generator to support inspectiondevices or cleaning heads for inspection or cleaning, and which is alsoretractable so that the inspection or cleaning heads are safely removedfor which the steam generator.

FIG. 2 shows an example of one type of cleaning head 50 designed tospray water from flow slot 52 about a support plate in the upper reachesof the steam generator. FIG. 3 shows a combined inspection/cleaningdevice including video camera 60 and nozzle 62 which may also bedeployed up through the flow slots in the support plates.

The prior art deployment system for such a combined inspection/cleaningdevice is shown in FIG. 4. Boom 70 is extended through access port 72and then uprighted within blowdown lane 74 as shown by arrow 76.Telescoping members 78, 80 extend from within cylinder 82 and deployinspection camera 84 upward. See U.S. Pat. No. 5,265,129.

As explained in the Background of Invention above, however, the distancebetween tube sheet 32, FIG. 1 and the first support plate 12 can be only18 inches. A device such as the boom and telescoping. cylinderscombination which in its collapsed state is only 18 inches tall andwhich must still extend up to 30 feet is difficult to design,manufacture, and control. Moreover, this design requires that the boom70 be placed inside the steam generator.

In contrast, the invention of this application includes an elongatedbody 80, FIG. 5 feedable through hand hole 82 from outside steamgenerator 84. Elongated body 80 is flexible enough to bend into positionto travel upwards as shown at 86 and also rigid in another configurationas shown at 88 for positioning cleaning head/inspection device 90 (seeFIGS. 2 and 3) up through the steam generator to reach the upper tubebundles.

There are some means 92 for driving elongated body 80 up through supportplates 12, 14, 16, 18, 22, 24, and 26, FIG. 1, and for retracting body80, FIG. 5, back down through the support plates.

In a preferred embodiment, elongated body 80, FIG. 5, is a “rigid chain”100, FIG. 6 driven by motor 102 and drive assembly 103 as it unfurlsfrom stack 104 in container 106. Turn shoe 108 directs rigid chain 100to turn upwards carrying inspection/cleaning head 110 to the upper twobundles of the steam generator. Rigid chain 100 is flexible enough tomake the bend shown at 109 but is also rigid enough to extend upwardsafter bend 108 and support cleaning and inspection equipment about theupper tube bundles some 30 feet from bend 108.

Other elongated bodies, however, are possible and are within the scopeof this invention so long as they are flexible in one configuration tobend into a position for extension up through the flow slots and rigidin another configuration for positioning and supporting cleaninghead/inspection devices up through the flow slots in the support platesof the steam generator. The various embodiments are discussed asfollows.

Rigid Chains

In one embodiment, there are two rigid chains 120 and 122, FIG. 7. Rigidchain 122 is constructed to bend in only one direction as shown in 124while rigid chain 120 is constructed to bend only in the oppositedirection as shown at 126. When placed back-to-back, the combination isrigid enough to be deployed upward supporting a cleaning head/inspectiondevice up through the flow slots in the tube support plates 128, 130,132, etc. Rigid chain 120 is deployed first in annulus 134 while rigidchain 122 is deployed first in annulus 136. Then, both chains are drivenby drive 138 through guide shoes 140 and 142 respectively.Video/cleaning fluid umbilical 144 is tensioned by tension arm 146.

As shown in FIG. 8, a typical non-rigid chain 150 is free to bend in twodirections. Rigid chain 152 a, FIG. 9, however, is free to bend in onlyone direction. When two such chains 152 b and 152 c, FIG. 10, are placedback to back, a rigid structure is formed from an assembly flexible inone configuration—namely, each chain by itself.

Another rigid chain is shown in FIG. 11A. Each link 160 is hollow tocarry video 162, cleaning spray 164, and power 166 umbilicals. Pin 168engages the adjacent link to prevent rotation of the links with respectto each other. Pin 168 also retracts to allow bending of link 172 withrespect to link 160.

In this embodiment, a pin drive 173, FIG. 11B is used to push theengagement pins in after the 90° turn is made providing a rigid support.The pin drive also pulls the engagement pins out upon retraction of therigid chain back down through the flow slots of the support plates ofthe steam generator. Pin drive 177 can be as simple as a set of leaftype springs that bear against the top of the pin 177, engaging it inthe hole, when pushed from the direction shown by arrow 175. When pin179 is pulled back, in the direction shown by arrow 181, the leafsprings bear under the pin head, disengaging it from the hole in thelinks.

In another embodiment, the rigid chain concept includes link 200, FIG.12, joined to link 202 by pins 204 and 206. Detent ball 208 on link 202engages a detent recess 210 on link 200. In this way, link 202 isnormally locked with respect to link 200 but upon the application of asufficient bending force (by pushing the chain through turn shoe 108,FIG. 6) detent ball 208 will be dislodged from detent recess 210 therebyallowing link 200 to pivot with respect to link 202 providing a flexibleconfiguration to bend into a position for extension up through the flowslots in the support plates of the interior of the steam generator.After the bend is made, the detent balls of one link again engage thedetent recesses of an adjacent link to provide a rigid configuration forpositioning and supporting inspection/cleaning devices up through thesteam generator proximate the upper tube bundles.

The design shown in FIG. 12 offers advantages over the paired rigidchain design shown in FIG. 7 in that only one set of links is requiredand also offers advantages over the pin configuration shown in FIG. 11since a pin engagement/retraction drive is not required. Also, in theconfiguration shown in FIG. 12, the hollow interior of links 200 and 202provide a passage for the umbilical subsystem.

In another embodiment, rigid chain 220, FIG. 13 includes links 222 and224 joined by ball and spring assembly 226. Spring 228 biases link 224to lock with respect to link 222 but upon the application of sufficientbending force (by pushing the chain through turn shoe 108, FIG. 6), thelinks can rotate with respect to each other to make the 90° turn shownat 86, FIG. 5. The closest analogy to this embodiment is a series oftent poles engaged by an elastic “bungie” cord running though the centerof the poles. After the 90° turn is made, the springs bias the linkstogether providing a rigid configuration for deployment up through thesteam generator.

In another embodiment, link 250, FIG. 14 includes rare earth magnet 252while link 254 includes ferrous plate 256. The magnet 252 of link 250 isattracted to ferrous plate 256 of link 254 thereby urging the links toremain locked together. A sufficient bending force, however, as with thedesigns shown in FIGS. 12 and 13, will allow the links to rotate withrespect to each other but will then engage again after bending of thechain. Rigid chain 260, FIG. 15, is a combination of both the springembodiment shown in FIG. 13 and the magnet embodiment shown in FIG. 14.

In another embodiment, rigid chain 280, FIG. 16, includes fairly lengthylinks 282, 284, and 286 each having an extension 290 as shown for link282 which prevents each adjacent link from rotating in one direction.These longer links minimize the total number of links required for thesystem.

Rigid Links

Another embodiment for elongated body 80, FIG. 5 which is flexible inone configuration and rigid in another configuration is a series ofrigid links, FIG. 17. Hollow rigid links 306, 308, 310 each includearticulation recesses 302 and 304 between adjacent links 306, 308, and310. In this embodiment, the articulation recess is only on one side ofeach link. Pivot pin 312 and articulation recess 302 allow link 306 torotate slightly with respect to link 308 in the direction shown by arrow314. Since each link can rotate slightly, the series of rigid links canmake the bend required to traverse the blowdown lane of the steamgenerator (See FIG. 1) but then also extend upward through the flowslots and in this configuration the assembly is fairly rigid since“backbone” portion 316 prevents the individual links from bending in thedirection shown by arrow 318.

A similar design is shown in FIG. 18 for rigid links 322, 326 and 328.In this case, each link 322, 324, and 326 comprises a hollow memberjoined to an adjacent link by elastomeric hinge element 330. Here, thereis an articulation recess 336 and 338 on each side of each elastomerichinge element. The series of links can bend enough to be driven down theblowdown lane and then turn upwards to extend up through the flow slots.Straightening cable 332 which passes through orifice 333 formed in eachlink is used to lock the links in a rigid configuration. Water umbilical334 and peripheral service lines 336 pass through the center of eachlink. These links may be made of any flexible plastic material.

Mast Embodiments

An alternative to the various rigid chain or rigid link embodimentsdescribed above is shown in FIG. 19. Extendable mast 360 is made of amaterial normally self-biased to form a tube as shown at 362 even thoughit can be fed off a flat roll 364. The material of mast 360 is typicallya 0.010 spring-tempered stainless steel available from Spar Aerospace9445 Airport Road, Brampton, Ontario, Canada. The natural aspect of thematerial is a 2″ diameter tube with plenty of overlap. The tube may bereinforced along its length by guide sleeves such as sleeve 364 asrequired.

As shown in FIG. 20, mast 360 guides water line 370 and peripheralservice lines 372 and 374 encased by jacketing material 376 up throughthe flow slots of the steam generator. Motor drive 378 drives thisembodiment of the deployment system up through the flow slots. Motordrive 378 includes counter rotating drums 380 and 382 each drivingplanetary guide roller arrangement 384. As an alternative, two rolls ofthe mast material may be used to form a tube—each roll forming half ofthe tube with plenty of overlap for extra rigidity.

Combined Mast/Rigid Link Embodiments

The mast shown in FIGS. 19-20 may used in conjunction with any of therigid chains or rigid links described above including the rigid linkembodiment 300, FIG. 17 as shown in FIG. 21 for additional support asthe rigid links are extended upward to the top of the steam generator.Mast storage drum 382, FIG. 21 includes the roll or rolls of mastmaterial and turning shoe 384 feeds the rigid links from outside thehand hole of the steam generator and ultimately up through the flowslots in the successive series of support plates.

In any embodiment of the elongated snake-like body of this invention,whether rigid chain or rigid link embodiments or the mast materialembodiment, or combinations thereof, the boom and telescopic cylindersof the prior art shown in FIG. 4 are eliminated and instead theelongated body is small enough so that it can be fed through the handhole of the steam generator and through the flow slots in successivesupport plates. The body is also fully retractable to prevent any riskof any component of the system from becoming lodged in the upper regionsof the steam generator. The body is flexible enough in one configurationto bend into a position for extension up through the flow slots insuccessive support plates and rigid in another configuration forpositioning and support cleaning head/inspection devices up about theupper tube bundles.

Accordingly, the instant invention in any embodiment achieves theseemingly mutually exclusive goal of providing a deployment device whichcan bend and which is also rigid enough after the bend to support acleaning head or an inspection device at a distance up to 30 feet withinthe steam generator.

Therefore, although specific features of this invention are shown insome drawings and not others, this is for convenience only as eachfeature may be combined with any or all of the other features inaccordance with the invention.

And, other embodiments will occur to those skilled in the art and arewithin the following claims:
 1. A deployment system for an upper bundlesteam generator cleaning/inspection device, said deployment systemcomprising: an elongated body feedable substantially horizontallythrough a lower access in a steam generator shell proximate the tubesheet of the steam generator, said elongated body flexible in oneconfiguration to bend into a position for extension vertically upthrough flow slots in support plates of the interior of the steamgenerator, and being structured and arranged to be rigid and not bend inany direction when vertically disposed for positioning and supportingcleaning/inspection devices up through the steam generator proximate theupper tube bundles of the steam generator; means for guiding theelongated body to bend from said substantially horizontal orientation tothe rigid vertical position; and means for driving said elongated bodyvertically up through said support plates and for retracting saidelongated body back down through said support plates.
 2. The deploymentsystem of claim 1 in which said elongated body assembly includes meansfor mounting a cleaning head on a terminal end thereof for cleaning theupper tube bundles of the steam generator.
 3. The deployment system ofclaim 1 in which said elongated body includes means for mounting aninspection camera on a terminal end thereof for inspecting the uppertube bundles of the steam generator.
 4. The deployment system of claim 1in which said elongated body is a rigid chain.
 5. The deployment systemof claim 4 in which said rigid chain includes a number of links, eachpivotable with respect to an adjacent link in one configuration, saidlinks including means for releasably locking adjacent links againstpivoting in another configuration.
 6. The deployment system of claim 5in which said means for releasably locking includes retractable pins forlocking said links together when engaged, and for freeing said linkswhen retracted.
 7. The deployment system of claim 6 in which said meansfor driving includes means for automatically retracting and engagingsaid pins.
 8. The deployment system of claim 5 in which said means forreleasably locking includes detent balls on one portion of said linksand complementary detent recesses on one portion of adjacent sets oflinks.
 9. The deployment system of claim 5 in which said means forreleasably locking includes a spring for urging one link to remainengaged with an adjacent link.
 10. The deployment system of claim 5 inwhich said means for releasably locking includes a magnet for urging onelink to remain engaged with an adjacent link.
 11. The deployment systemof claim 5 in which said means for releasably locking includes both aspring and a magnet for urging one link to remain engaged with anadjacent link.
 12. The deployment system of claim 4 in which said rigidchain includes a plurality of links each having a hinge and a portionextending beyond said hinge for preventing movement of an adjacent linkin one direction.
 13. The deployment system of claim 1 in which saidelongated body comprises a pair of rigid chains, each bendable in onlyone direction, each deployed into the steam generator by bending, thepair deployed back to back in the rigid configuration.
 14. Thedeployment system of claim 1 in which said elongated body comprises apair of rigid chains, each chain free to bend in one direction but rigidin the opposite direction.
 15. The deployment system of claim 13 furtherincluding means for orientating said pair of rigid chains back to backthereby providing a rigid structure for positioning and supportingcleaning/inspection devices up through the steam generator.
 16. Thedeployment system of claim 1 in which said elongated body includes aplurality of rigid links.
 17. The deployment system of claim 16 in whichsaid links each have a hinge and at least one articulation recessproximate said hinge for allowing movement of an adjacent link in onlyone direction.
 18. The deployment system of claim 17 in which said linksincludes an articulation recess on each side of said hinge.
 19. Thedeployment system of claim 1 in which said elongated body includes anextendable mast formed of a material self-biased to form a tube.
 20. Thedeployment system of claim 19 in which said means for driving includes apair of counter-rotating drums for driving said mast material engagedbetween said drums.
 21. The deployment of system of claim 1 in whichsaid elongated body comprises a rigid chain supported by an extendablemast formed of a material self-biased to form a tube.
 22. The deploymentsystem of claim 1 in which said elongated body comprises a series ofrigid links supported by a mast formed of a material self-biased to forma tube.
 23. The deployment system of claim 1 in which said drive meansincludes a turning shoe for directing said elongated body from aposition proximate the tube sheet to a position for extension upwardstherefrom to the upper bundles of the steam generator.
 24. A deploymentsystem for an upper bundle steam generator cleaning/inspection device,said deployment system comprising: first and second rigid chainsincluding a number of links, each pivotable with respect to an adjacentlink when in a non-vertical configuration for bending into a positionfor travel up through the interior of the steam generator, said firstand second rigid chains being structured and arranged when combined tonot bend in any direction when vertically disposed; and means forreleasably locking adjacent links against pivoting when in the verticalconfiguration for positioning and supporting cleaning/inspection devicesup through the interior of the steam generator.
 25. The deploymentsystem of claim 24 in which said means for releasably locking includesretractable pins for locking said links together when engaged, and forfreeing said links when retracted.
 26. The deployment system of claim 24in which said means for releasably locking includes detent balls on oneportion of said links and complementary detent recesses on one portionof adjacent sets of links.
 27. The deployment system of claim 24 inwhich said means for releasably locking includes a spring for urging onelink to remain engaged with an adjacent link.
 28. The deployment systemof claim 24 in which said means for releasably locking includes a magnetfor urging one link to remain engaged with an adjacent link.
 29. Thedeployment system of claim 24 in which said means for releasably lockingincludes both a spring and a magnet for urging one link to remainengaged with an adjacent link.
 30. A system for inspecting or cleaningthe upper bundles of a steam generator, the system comprising: adeployment system including an elongated body feedable substantiallyhorizontally through a lower access in a steam generator shell proximatethe tube sheet of the steam generator, said elongated body flexible inone configuration to bend into a position for extension vertically upthrough the flow slots in support plates of the interior of the steamgenerator and structured and arranged to be rigid and not bend in anydirection when vertically disposed for positioning and supportingcleaning/inspection devices up through the steam generator proximate theupper tube bundles of the steam generator; a head attached to a distalend of the elongated body which extends substantially horizontally fromthe distal end of the elongated body when the elongated body is extendedvertically and the distal end thereof is proximate the upper tubebundles of the steam generator; means for guiding the elongated body tobend from the substantially horizontal orientation to the rigid verticalposition; and means for driving said elongated body vertically upthrough said support plates and also for retracting said elongated bodyback down through said support plates.
 31. A system for inspecting orcleaning the upper bundles of a steam generator, the system comprising:a deployment system including an elongated body feedable substantiallyhorizontally through a lower access in a steam generator shell proximatethe tube sheet of the steam generator, said elongated body flexible inone configuration to bend into a position for extension vertically upthrough the flow slots in support plates of the interior of the steamgenerator and structured and arranged to be rigid and not bend in anydirection when vertically disposed for positioning and supportingcleaning/inspection devices up through the steam generator proximate theupper tube bundles of the steam generator, a head attached to a distalend of the elongated body which extends substantially horizontally fromthe distal end of the elongated body when the elongated body is extendedvertically and the distal end thereof is proximate the upper tubebundles of the steam generator; and means for driving said elongatedbody vertically up through said support plates and also for retractingsaid elongated body back down through said support plates.
 32. A systemfor inspecting or cleaning the upper bundles of a steam generator, thesystem comprising: a deployment system including an elongated bodyfeedable substantially horizontally through a lower access in a steamgenerator shell proximate the tube sheet of the steam generator, saidelongated body flexible in one configuration to bend into a position forextension vertically up through the flow slots in support plates of theinterior of the steam generator and structured and arranged to be rigidand not bend in any direction when vertically disposed for positioningand supporting cleaning/inspection devices up through the steamgenerator proximate the upper tube bundles of the steam generator; ahead attached to a distal end of the elongated body which extendssubstantially horizontally from the distal end of the elongated bodywhen the elongated body is extended vertically and the distal endthereof is proximate the upper tube bundles of the steam generator; andmeans for guiding the elongated body to bend from the substantiallyhorizontal orientation to the rigid vertical position.
 33. A deploymentsystem for an upper bundle steam generator cleaning/inspection device,said deployment system comprising: a first rigid chain free to bend inonly one direction and including a number of links, each pivotable withrespect to an adjacent link when in a non-vertical configuration forbending into a position for travel up through the interior of the steamgenerator; and a second rigid chain free to bend only in a directionopposite the first rigid chain and including a number of links, eachpivotable with respect to an adjacent link when in a non-verticalconfiguration for bending into a position for travel up through theinterior of the steam generator; wherein the first and second rigidchains are placed back-to-back to form a rigid structure when verticallydisposed for positioning and supporting cleaning/inspection devices upthrough the interior of the steam generator.